1. Field of the Invention
The invention relates to a light bar structure and a display device and, more particularly, to a light bar structure and a display device capable of providing a uniform light field.
2. Description of the Prior Art
Since liquid crystal display (LCD) device has advantages of light weight, thin thickness, low power consumption and no radiation, it has been popularly applied to laptop computer, personal computer, television and so on. However, because an LCD panel of the LCD device cannot emit light by itself, a backlight module is needed to provide sufficient illumination for the LCD panel, so as to enable the LCD panel to display images.
Referring to FIG. 1, FIG. 1 is an exploded view illustrating an LCD device 1 of the prior art. As shown in FIG. 1, the LCD device 1 comprises an outer frame 10, a display panel 12, a backlight module 14 and a back cover 16. The display panel 12 is disposed on the backlight module 14. The display panel 12 has an active area 120. The backlight module 14 comprises a frame 20, an optical film assembly 22, a light guide plate 24, two light bar structures 26 and a reflective sheet 28. The optical film assembly 22 is disposed on the light guide plate 24. The reflective sheet 28 is disposed under the light guide plate 24. The two light bar structures 26 are disposed at opposite sides of the light guide plate 24 respectively. Each of the light bar structure 26 consists of a plurality of light emitting diodes 260 and a circuit board 262. Light emitted from the light emitting diodes 260 is projected out of the optical film assembly 22 via the light guide plate 24. The display panel 12 and the backlight module 14 are fixed within the outer frame 10 and the back cover 16, so as to assemble the LCD device 1.
Referring to FIG. 2, FIG. 2 is an enlarged view illustrating a partial area B shown in FIG. 1. As shown in FIG. 2, the light bar structure 26 comprises a plurality of light emitting diodes 260 and a circuit board 262. The light emitting diodes 260 are disposed on the circuit board 262. Each of the light emitting diodes 260 comprises a main body 2600 and a pair of leads 2602. Furthermore, the main body 2600 has a light emitting surface 2604 and the light emitting diode 260 emits light from the light emitting surface 2604. In general, each of the light emitting diodes 260 is fixed on the circuit board 262 by surface mount technology (SMT). Since the light emitting diodes 260 are disposed on the circuit board 262, a total thickness of each light bar structure 26 is equal to the sum of a thickness of the circuit board 262 and a height of each light emitting diode 260.
Referring to FIG. 3 along with FIG. 1, FIG. 3 is a partial top view illustrating the display device 12 and the light bar structure 26 shown in FIG. 1. As shown in FIG. 3, a distance A is between the light emitting surface 2604 of the light emitting diode 260 and an edge of the active area 120 of the display panel 12, and a span P is between two adjacent light emitting diodes 260. Light emitted from the light emitting surface 2604 of the light emitting diode 260 will form a fan-shaped light field. The larger the distance A is and the more uniform the fan-shaped light field spreads into the light guide plate 24. If the distance A between the light emitting diode 260 and the active area 120 is too small, a bright area will appear on the light emitting surface 2604 of the light emitting diode 260 and a dark area will appear between two adjacent light emitting diodes 260. Consequently, a hot spot phenomenon may occur at the edge of the active area 120. However, if the distance A increases due to the conventional light bar structure 26, the whole size of the backlight module 14 will increase correspondingly. On the other hand, another method for modifying the hot spot phenomenon is to increase the number of light emitting diodes 260 (i.e. to decrease the span P). However, if the number of light emitting diodes 260 increases, the production cost of the backlight module 14 will increase correspondingly.